In the past, a radar apparatus mounted on a vehicle emits a transmission wave from a transmission antenna and receives a reflected wave from a target, which reflects the emitted transmission wave, at a reception antenna to thus derive a target position and the like with respect to the vehicle (radar vehicle). The detailed processing thereof is as follows. A signal processing unit of the radar apparatus generates a beat signal by mixing a transmission signal corresponding to the transmission wave of which a frequency is changed with a predetermined period and a reception signal corresponding to the reflected wave. That is, the signal processing unit generates the beat signal based on a difference frequency (beat frequency) between the transmission signal and the reception signal in each of an UP section in which the frequency ascends with a predetermined period and a DOWN section in which the frequency descends.
Then, the signal processing unit generates a signal (hereinafter, referred to as a ‘converted signal’) with respect to each frequency by performing FFT (Fast Fourier Transform) for the beat signal. From the converted signals, the signal processing unit extracts a signal exceeding a threshold value of a predetermined signal level as a peak signal. Then, the signal processing unit derives paired data by pairing the peak signal of the UP section and the peak signal of the DOWN section based on a predetermined condition.
Then, the signal processing unit derives a distance (hereinafter, referred to a longitudinal distance) from the vehicle to the target or a distance (hereinafter, referred to as a transverse distance) of the target with respect to the vehicle in a direction substantially orthogonal to a traveling direction of the vehicle. Also, the signal processing unit derives a relative speed of the target with respect to the vehicle. In this way, the signal processing unit derives the position information of the target including the longitudinal and transverse distances of the target and the relative speed thereof, based on the paired data.
Then, the signal processing unit performs determination (hereinafter, referred to as ‘continuity determination’) processing of determining whether there is a temporally continuous relation between paired data (hereinafter, referred to as ‘this time paired data’) by this time processing and paired data (hereinafter, referred to as ‘previous time paired data’) by previous time processing. A case where there is a temporally continuous relation between both the paired data includes a case where data (hereinafter, referred to as ‘predicted paired data’), which is obtained by predicting this time paired data based on the previous time paired data, is generated and difference values of the longitudinal distances, transverse distances and relative speeds of this time paired data and the predicted paired data are within predetermined values.
When the paired data having the temporally continuous relation is derived consecutively a predetermined number of times, for example, three times of this time, previous time and the time before last, the paired data is decided as a target and target information including the position information and relative speed of the target is output to a vehicle control device that controls behaviors of the vehicle. As a result, the vehicle control device performs required vehicle control in accordance with the information of the decided target that is output from the radar apparatus. For example, Patent Document 1 discloses a technology relating to the continuity determination.    Patent Document 1: Japanese Patent Application Publication No. 2012-013484A
However, when a plurality of targets exists at the periphery of the vehicle and the reception antenna receives the reflected waves from the plurality of targets at the same time, a plurality of peak signals is extracted on a frequency axis in the UP and DOWN sections after the FFT processing. Also, not only the peak signals corresponding to the targets but signals due to noises individually appear in the vicinity of the frequencies of the peak signals. When the signals due to the noises exceed a threshold value, the signals are extracted as peak signals. In this way, when the peak signals exist on the frequency axis of the UP and DOWN sections, paired data (hereinafter, referred to as ‘mis-paired data’) paired in an incorrect combination other than a correct combination may satisfy a condition of paired data (hereinafter, referred to as ‘normal-paired data’) paired in a correct combination.
When the mis-paired data is derived, the false position information or relative speed different from the position information or relative speed of the target actually existing is output to the vehicle control device. In this case, since the vehicle control device controls the vehicle on the basis of the false position information or relative speed, the required vehicle control may not be performed or unnecessary vehicle control may be performed.
In particular, for example, when the vehicle is traveling in a tunnel or in the vicinity of a road side object such as a guard rail, a plurality of peak signals based on reflected waves from the road side object is detected, so that a possibility of the mis-pairing is increased. Like this, in the situation where the possibility of the mis-pairing is high, a possibility that the mis-paired data having a temporally continuous relation will be derived consecutively three times is also increased. When the mis-paired data is derived consecutively three times, a target that does not originally exist is decided as a moving object (i.e., a ghost is detected). Thereby, the vehicle control is performed while erroneously considering that a preceding vehicle exists.